SLIDE 1
Current Status of a Measurement of Hadronic Parity Violation in the Capture of Cold Neutrons
- n Helium-3
Current Status of a Measurement of Hadronic Parity Violation in the - - PowerPoint PPT Presentation
Current Status of a Measurement of Hadronic Parity Violation in the - - PowerPoint PPT Presentation
Current Status of a Measurement of Hadronic Parity Violation in the Capture of Cold Neutrons on Helium-3 for the n3He Collaboration Mark McCrea University of Manitoba 2015 CAP Congress June 18, 2015 Introduction Motivation Spallation
SLIDE 2
SLIDE 3
n3He Introduction
n3He probes the low energy strong interaction, using the weak interaction by measuring the parity violating directional asymmetry in the proton recoil from the reaction
- n +3He → p + T + 765keV
Beam n
3He
p θs,
k
T The goal of the experiment is to measure the asymmetry to the 2 × 10−8 level.
SLIDE 4
Theoretical Motivation
q q q q g Strong Interaction q q q q Z 0,W ± Weak Interaction u d d u d d u d d u d d ? Uncertain HWI N N N N PC Strong PV Weak π, ρ, ω DDH Parameterization DDH Meson Exchange Parameters: Opv = a1
πh1 π + a0 ρh0 ρ + a1 ρh1 ρ + a2 ρh2 ρ + a0 ωh0 ω + a1 ωh1 ω
SLIDE 5
A Brief Look at Parity
Under a parity transformation P polar vectors such as the momentum transform as P( kn) → − kn and P( kp) = − kp but axial vectors, such as the neutron spin, remain unchanged P( sn) → sn Orignal State:
Beam n
3He
p
θs,
k
T
Parity Transformed:
Beam n
3He
p
θs,
k
T
Spin Flipped:
Beam n
3He
p
θs,
k
T
SLIDE 6
Spallation Neutron Source
◮ Located at the Oak Ridge National Laboratory (ORNL) in
Tennessee
◮ 60 Hertz pulsed spallation source ◮ approximately 1010 neutrons/second ◮ n3He is running at the FnPB ◮ Three 20K liquid hydrogen moderator for cold neutron beam
lines
SLIDE 7
n3He Schematic Diagram
Biological Shielding Neutron Guide C1 C2 M1 SMP RFSF Collimator
3He Target/
Detector HF Solendoid
SLIDE 8
n3He Target Chamber
Beam
HV Signal 17 HV Frames with 8 wires each 16 signal Frames with 9 wires each
SLIDE 9
Assembled Frame Stack
◮ 17 HV frames ◮ 16 signal frames ◮ 9 signal wires per frame ◮ 144 signals to read out
SLIDE 10
Proton Asymmetry in Chamber
- n +3He → p + T + 765keV
Neutron Proton Triton Electron Collection
A proton and triton asymmetry occur in the chamber but the longer range of the proton causes its asymmetry to dominate
SLIDE 11
Target Chamber on Stand
◮ 4 point adjustable stand ◮ roll, pitch, height were not
independent
◮ target electrically isolated
from stand
◮ angle block used for initial
alignment
SLIDE 12
Components on Beamline
SLIDE 13
First Data from Ion Chamber
SLIDE 14
Ion Chamber Simulation - Garfield++
Garfield++ is a toolkit for the detailed simulation of particle detectors that use gas and semi-conductors as sensitive medium.
◮ Gas properties calculated using Magboltz ◮ Ion Mobility from Data from Atomic Data and Nuclear Data
Tables 17, 177-210 (1976)
◮ Signal calculated with Shockley-Ramo Theorem:
i(t) = −qv · Ew(r)
◮ Ew(r) is a calculated weighting field as though the electrode
had a potential of 1V and everything else is ignored
◮ Fields and Electrode locations from Gmsh and Elmer ◮ Looking at charge collection times and signals
SLIDE 15
Geometry - Gmsh
SLIDE 16
Geometry - Gmsh
SLIDE 17
Fields - Elmer FEM
SLIDE 18
Initial Simulation Details
◮ 200 events at 6 locations
spaced evenly between HV and Signal wire
◮ ion and electron
propagated from each point
◮ collection time to be
compared with measured values
SLIDE 19
Collection Times
t(ns)
500 1000 1500 2000 2500 3000 3500 4000 20 40 60 80 100 120
Electron Collection Times
◮ Six equally spaced starting positions gave 6 peaks. ◮ 200 electrons per positions
SLIDE 20
Integrated Signal - electron
hIntegratedSig-e-0
Entries 200 Mean -22.85 RMS 0.7114
- 6
10 × fC
- 25
- 24
- 23
- 22
- 21
- 20
5 10 15 20 25
hIntegratedSig-e-0
Entries 200 Mean -22.85 RMS 0.7114 hist Integrated Signal e -0
hIntegratedSig-e-1
Entries 200 Mean -71.36 RMS 1.393
- 6
10 × fC
- 74
- 72
- 70
- 68
- 66
2 4 6 8 10 12 14 16
hIntegratedSig-e-1
Entries 200 Mean -71.36 RMS 1.393 hist Integrated Signal e -1
hIntegratedSig-e-2
Entries 200 Mean -108.7 RMS 2.172
- 6
10 × fC
- 114 -112 -110 -108 -106 -104 -102
2 4 6 8 10 12 14 16
hIntegratedSig-e-2
Entries 200 Mean -108.7 RMS 2.172 hist Integrated Signal e -2
hIntegratedSig-e-3
Entries 200 Mean -126.5 RMS 2.433
- 6
10 × fC
- 132 -130 -128 -126 -124 -122 -120
2 4 6 8 10 12 14
hIntegratedSig-e-3
Entries 200 Mean -126.5 RMS 2.433 hist Integrated Signal e -3
hIntegratedSig-e-4
Entries 200 Mean -140.2 RMS 2.506
- 6
10 × fC
- 146 -144 -142 -140 -138 -136 -134
2 4 6 8 10 12
hIntegratedSig-e-4
Entries 200 Mean -140.2 RMS 2.506 hist Integrated Signal e -4
hIntegratedSig-e-5
Entries 200 Mean
- 149.4
RMS 27.27
- 6
10 × fC
- 150
- 100
- 50
20 40 60 80 100
hIntegratedSig-e-5
Entries 200 Mean
- 149.4
RMS 27.27 hist Integrated Signal e -5
Ion/Electron pair signals measure from 6 positions
SLIDE 21
Summary
◮ Target chamber assembled and tested November 2014 ◮ Target chamber installed December 2014 ◮ First Data from Chamber January 2015 ◮ Data taking to continue until end of 2015 ◮ Charge collection simulations are progressing
SLIDE 22
n3He Collaboration
Duke University, Triangle Universities Nuclear Laboratory ◮ Pil-Neo Seo Istituto Nazionale di Fisica Nucleare, Sezione di Pisa ◮ Michele Viviani Oak Ridge National Laboratory ◮ Seppo Penttil¨ a ◮ David Bowman ◮ Vince Cianciolo ◮ Jack Thomison ◮ Paul Mueller University of Kentucky ◮ Chris Crawford ◮ Latiful Kabir ◮ Aaron Sprow Western Kentucky University ◮ Ivan Novikov University of Manitoba ◮ Michael Gericke ◮ Mark McCrea ◮ Carlos Olguin Universidad Nacional Aut´
- noma de M´